Curing behaviour of syndiotactic polystyrene-epoxy blends: 1. Kinetics of curing and phase separation process

The modification of the curing behaviour and the phase separation process for an epoxy resin blended with a crystalline thermoplastic was investigated in the case of the diglycidylether of bisphenol-A (DGEBA)/4,4'-methylene bis(3-chloro-2,6-diethylaniline) (MCDEA) blended with syndiotactic polystyrene (sPS) and cured at 220 degreesC. Phase separation taking place during curing of the blend was investigated by differential scanning calorimetry (DSC) and optical microscopy in order to get a better understanding of the complex interactions between cure kinetics of epoxy matrix and crystallisation of sPS, both influenced by blend composition. Results suggested that phase separation and crystallisation of sPS occurred at almost similar times, with phase separation just being ahead of crystallisation. DSC and near-infrared measurements were used for the determination of the cure kinetics. Slow delays on the cure reactions were observed during the first minutes for the sPS-containing blends compared with the neat DGEBA/MCDEA system but, after some time, the reaction rate became faster for the blends than for the neat matrix. Phase separation occurring in the mixtures may explain this particular phenomenon. (C) 2004 Society of Chemical Industry